1. Field of the Invention
The present invention is directed to hydrogen gettering structure including a titanium member (in particular, a titanium bulk member); to packaging (module) components (for example, a lid, a container, etc.) for packaging semiconductor devices (for example, microelectronic semiconductor devices) and packages (modules) formed, including the hydrogen gettering structure (for example, a semiconductor device module containing the hydrogen gettering structure); and to methods of forming the hydrogen gettering structure and packaging components and packages. The present invention is especially directed to hydrogen gettering structure, and module components and modules having such structure, and methods for forming such structure and components and modules, which avoid damage and degradation of articles (for example, semiconductor devices containing III-V semiconductor materials) contained in such modules, due to hydrogen in the modules.
Thus, the present invention is particularly directed to hydrogen gettering structure, and components and modules using such hydrogen gettering structure, which avoid damage and degradation of articles sought to be protected from hydrogen in the environment of the article. For example, the present invention is directed to hydrogen gettering structure, and to module components and modules, which avoid hydrogen degradation of semiconductor devices in the modules, particularly those devices having a low threshold hydrogen level in hermetic (air-tightly sealed) packages.
More generally, the present invention is directed to hydrogen gettering structure having a bulk getter for absorbing hydrogen. While the present invention will be described primarily in connection with hydrogen gettering structure for packaged semiconductor devices, the present invention is not limited thereto, and can be utilized in connection with other structure in which hydrogen gettering is necessary and/or desired (for example, nuclear reactor structure).
2. Discussion of the Related Art
A problem experienced by semiconductor manufacturers, in connection with packaged semiconductor devices, is hydrogen degradation of the devices in hermetically sealed packages. The hydrogen within the packages can be generated from various parts of a package, for example, from housing materials, plated nickel layers, Eccosorb (a material used in semiconductor packages of, e.g., millimeter wave integrated circuits (MMICs), to absorb electrical signals), epoxy adhesives, etc.
It has been proposed to mitigate the problem of hydrogen degradation by baking out housing materials prior to populating the semiconductor device in the package and hermetically sealing. While this has been successful in some instances, such technique to mitigate the problem of hydrogen degradation has not been sufficient, particularly with devices having a low hydrogen threshold level.
Another technique for overcoming this problem with hydrogen degradation involves suspending inorganic hydrogen-absorbing material in silicone, in the device package. The inorganic hydrogen absorption material can be any of known metal oxide hydrogen getters. However, this technique has problems when utilized in packaging, e.g., microelectronic devices. For example, the material used undesirably takes up a large amount of moisture, requiring careful handling during the package sealing process. In addition, silicone may vaporize and contaminate electronic device and laser seal surfaces, and additional problems arise with the packaged device due to mobile impurity ions introduced due to including this hydrogen-absorbing material in silicone in the device package.
U.S. Pat. No. 6,110,808 to Saito discloses another technique for gettering hydrogen in semiconductor packages. This technique includes sequentially depositing metal layers on a package component, the sequentially deposited metal layers including palladium as the outermost layer and zirconium or titanium adjacent thereto. The contents of U.S. Pat. No. 6,110,808 are incorporated herein by reference in their entirety.
While this technique in U.S. Pat. No. 6,110,808 provides hydrogen gettering, a problem exists that in forming, e.g., titanium hydrides to achieve the hydrogen gettering (that is, achieve absorption of hydrogen), the titanium hydride increases in volume and can cause a problem that the layers fall off the package component.
U.S. patent application Ser. No. 09/415,513, filed Oct. 8, 1999, the contents of which are incorporated herein by reference in their entirety, discloses a hydrogen gettering element, which is a bulk gettering element. This element includes a bulk member of titanium, which has an outer surface that is substantially free from oxide, secured to one of the interior surfaces of a package component. This patent application discloses that a thin layer of palladium can be formed on the outer surface of the titanium, to prevent the titanium from oxidizing. Hydrogen atoms in the interior of the housing chemically combine with the titanium, such that the interior of the housing is substantially free from hydrogen, thus improving electrical properties and life of the microelectronics device within the package.
While the foregoing techniques have been utilized for hydrogen gettering, it is desired to provide structure achieving improved and increased hydrogen gettering, in structure which is stably provided in the interior of, e.g., a semiconductor package, and which can be simply and inexpensively manufactured.
Applicants have developed hydrogen gettering structure providing increased hydrogen gettering, while being easily manufactured and being inexpensive. Applicants have found that structure including a member of a metal for absorbing hydrogen, with a metal-doped palladium layer on a surface thereof, the metal dopant being selected from the group consisting of silver, rubidium and rhodium and being included in an amount sufficiently low such that the metal dopant does not form an alloy with the palladium, the metal for absorbing hydrogen being different than palladium, provides a simple and effective hydrogen gettering element, while being inexpensive and easy to manufacture. This hydrogen gettering structure, for example, when utilized in connection with a packaged semiconductor device (semiconductor device module), is included within the package (module) and attached to a package component (for example, a lid of the package), with the member of the metal for absorbing hydrogen being closer to the package component than the metal-doped palladium layer (for example, the metaldoped palladium layer being exposed to the interior of the package). Illustratively, and not to be limiting, the metal for absorbing hydrogen can desirably be titanium (or zirconium), and the metal-doped palladium layer includes at least 0.1% by weight of the metal dopant (for example, and not to be limiting, includes 0.1%-10% by weight of the metal dopant).
According to the present invention, and not to be limiting thereof, by doping, e.g., silver (Ag:4 d10 5 s1) into palladium (Pd:4 d10), the 5 s1 energy state of silver, which contains 1 electron, will activate the 5 s0 empty energy state of palladium and the 4 p0 empty energy state of palladium. These energy states will hybridize to form 10 s0.5 p1 d1.4 hybrid energy states. In each hybrid energy state, the hybrid electron will couple with one electron of hydrogen to increase the hydrogen holding lifetime. Following this, the hydrogen atoms will be transferred to the, e.g., titanium underlayer because the titanium has a lower energy state, and the hydrogen is then converted to titanium hydride in the titanium underlayer, forming a stable titanium hydride. Using the, e.g., silver-doped palladium, hydrogen gettering capacity of palladium increases at least 10 times as compared to using pure palladium, as a surface coating on the titanium.
As indicated previously, III-V semiconductor materials, as well as related materials, are very sensitive to hydrogen. Modules (packages) such as photonics transmitters, receivers, and ultra-high speed/large bandwidth DWDM (dense wavelength division multiplexing) modules for wireless communications contain III-V semiconductor materials and related MMIC chips (such as semiconductor lasers, photodetectors, low noise amplifiers (LNAs) and trans-impedance amplifiers (TIAs)). Hydrogen residue in the sealed modules increase surface ion migration on the chips during operation, causing degraded performance and reduced life. By incorporating the hydrogen gettering structure according to the present invention in such modules, degradation of device performance and reduction of device life due to hydrogen is reduced, to improve device performance and reliability.
Thus, according to the present invention, the above-described hydrogen gettering structure, containing, for example, a titanium bulk member and a layer of, e.g., silver-doped palladium on the surface thereof, can be affixed to a module component and incorporated in the module to provide hydrogen gettering, improving device performance and reliability. The hydrogen gettering structure of the present invention can also be incorporated in various other structures where hydrogen gettering is necessary or desired (for example, in nuclear reactor structure).
According to the present invention, the hydrogen gettering structure according to the present invention can be easily and inexpensively manufactured. For example, a bulk member (e.g., sheet) of the metal for absorbing hydrogen (for example, titanium), can be provided, and a metal-doped palladium layer, the metal dopant being, for example, silver, rubidium and/or rhodium, deposited on the member of the metal for absorbing hydrogen. The deposition of the metal-doped palladium layer can be achieved by, e.g., sputtering, using, for example, a target of palladium and the metal dopant. Other techniques for depositing the metal-doped palladium layer can also be utilized, including, but not limited to, vacuum evaporation (for example, electron beam evaporation). Prior to depositing the metal-doped palladium layer, it is effective to clean the titanium bulk member (e.g., titanium metal sheet), and to remove the top titanium oxide film so that the, e.g., silver-doped palladium layer is deposited in direct contact with the titanium.
According to the present invention, the hydrogen gettering structure can be affixed to the module component by any of various techniques, including soldering or via an epoxy resin layer (epoxy adhesive).
Accordingly, by the present invention, hydrogen gettering structure is provided having improved gettering, and which can easily and effectively be manufactured at low cost, providing increased hydrogen gettering capacity of the titanium bulk member. Incorporating such hydrogen gettering structure in a packaged semiconductor module, device performance and reliability are improved.